In 1943, NRL developed monopulse radar, now the basis for all modern tracking and missile control radars. The monopulse technique was first applied to the Nike-Ajax missile system, which at the time was the nation's continental air defense system. Monopulse radar eventually led to the development of the AN/FPS-16, the first high-precision monopulse instrumentation radar. In 1958, this radar was used to guide the launchings of the first U.S. space satellites at Cape Canaveral. Monopulse radar is still the most widely used technique for military tracking radar because of its high accuracy and relative immunity to electronic countermeasures that degrade other tracking methods.